When a man is to shot with an image capturing apparatus such as a digital still camera, the image capturing apparatus-must be focused to the man's face serving as a main object, and the image of the man's face serving as a main object must be captured at an optimal exposure. In conventional AF/AE (Auto Focus/Auto Exposure) control, a predetermined area in the frame is defined as a distance measuring/photometry area, and the focus and exposure are adjusted to the distance measuring/photometry area. If the man's face serving as a main object falls outside the distance measuring/photometry area, the focus and exposure do not match the man's face.
For example, when the center of the frame is set as a distance measuring/photometry area, and an image is captured with a composition in which two mans exist side by side, as shown in FIG. 5A, or a composition in which a man shifts to right within the frame, as shown in FIG. 5B, the focus and exposure are adjusted to the background of the man. In FIGS. 5A and 5B, a broken frame is a distance measuring/photometry area. To prevent this, there are proposed many control methods of detecting the position of a man's face from a captured image, extracting an AF/AE evaluation value from the detected region, and adjusting the focus and exposure (see, e.g., Japanese Patent Laid-Open Nos. 05-041830, 2001-119622, 2003-107335, and 2003-107555).
In Japanese Patent Laid-Open No. 05-041830, a skin tone is obtained from a captured image, and if the skin tone is determined to be a man's face, the exposure is so controlled as to set the average luminance signal level to a desired value in the skin tone of a subsequently captured image. That is, a captured image for detecting the position of a man's face and a captured image for detecting an evaluation value used for exposure control are different.
Japanese Patent Laid-Open Nos. 2001-119622 and 2003-107335 disclose a control method of adjusting the exposure to a man's face in a captured image, and Japanese Patent Laid-Open No. 2003-107555 discloses a control method of adjusting the focus to a man's face in a captured image. However, these references do not describe whether a captured image for detecting the position of a man's face and a captured image for detecting an AF/AE evaluation value are the same.
However, a certain time is required to detect the position of the man's face. Even when the position of the man's face is detected from the captured image to set a distance measuring/photometry area, and an AF/AE evaluation value is detected from a subsequently captured image, the man's face falls outside the distance measuring/photometry area, and the focus and exposure fail to match the man's face, if the man moves or camera shake of the image capturing apparatus occurs.
For example, a case in which a man who moves from left to right within the frame is shot to successively capture images of two frames, as shown in FIGS. 6A and 6B will be explained. For example, FIG. 6B shows an image captured when 1 sec has elapsed from the timing shown in FIG. 6A.
The results of detecting the position of a man's face from images in FIGS. 6A and 6B are x and y regions surrounded by dotted lines. The x region determined from the image of FIG. 6A to be the position of the man's face is set as a distance measuring/photometry area, and an AF/AE evaluation value is detected from the subsequently captured image of FIG. 6B. In FIG. 6B, the position of the man's face moves to the y region. If AF/AE control is performed on the basis of the AF/AE evaluation value detected from the x region, the focus and exposure are adjusted to an object which exists on the background in the x region and is irrelevant to the man.